System of control for tandem rolling-mills and the like.



W. R. CLARK.

SYSTEM OF CONTROL FOR TANDEM ROLLING MILLS AND '[HE LIKE APPLICATIONFILED 16.22. I912.

1,267,184. Patented May 21, 1918.

2 SHETSSHEET I.

WITNESSES:

1N VEN TOR.

W. R. CLARK.

SYSTEM OF CONTROL FOR TANDEM HQLLING MILLS AND THE LIKE.

APPLICATION FILED AUG-22.1912.

1 ,26'7, 1 84:. Patented May 21, 1918.

I 2 SHEETS-SHEET 2- /7 .4. 20

IVITNESSES:

7/f W'y [.VVENTOR.

A TTORNEKP,

UNITED STATES PATENT OFFICE.

WALTER B. CLARK, 0F BRIDGEPOBT, CONNECTICUT, ASSIGNOR T0 BRIDGEPORTBRASS COMPANY, OF BRIDGEPORT, CONNECTICUT, A CORPORATION OF CONNECTICUT.

l SYSTEM OF CONTROL FOR TANDEM ROLLING-MILLS AND THE LIKE.

Specification of Letters Patent.

Patented May 21, 1918.

Application filed August 22, 1912. Serial at. 716,435.

To all whom it ma concern:

Be it known tiat I, WALTER R. CLARK, a citizen of the United States,residin in Bridgeport, county of Fairfield, and tate of Connecticut,have invented certain new and useful Improvements in Systems of Controlfor Tandem Rolling-Mills and the like, of which the following is a full,clear, and exact description.

This invention relates to a system of controlling the relative speeds ofrolling mills or similar metal working devices arranged in tandem, wherethe bar or sheet is acted on by the respective devices simultaneous y.The improved system is especially applicable to tandem mills for rollingmaterial of medium and heavy gage, so heavy in fact, that a considerabletension may be put u on the rolled bar, in addition to that exerte by apair-of rolls in rolling it, without strainin it beyond its elasticlimit.

eretofore, in rolling sheets or bars of brass or other metal by means ofindividually driven tandein mills, it has been customary to rely solelon manual control of the speed of the in ividual mills. For example, iftwo individually driven stands of rolls are arranged in tandem fashion,to successively reduce the bar or sheet, it is usual merely to providehand operated speed controlling devices whereby the operator mayregulate individually the speed of the respective prime movers or motorsdriving the respective mills. Where this manual control is the onl oneprovided, however, considerable di culty is encountered in distributinproperl the total work of reduction of t e metal etween the individualpairs of rolls. For instance, if one of the mills slows down from anyexternal cause, or if it speeds u or slows down as a result of a changein t e gage of the material bein rolled due to the expansion of therolls or 518.111 spots in the metal, or other causes, it is a verydifiicultmatter, in fact practically impossible, to control manually thespeed of the other mill in consonance with the irregular speedvariations of the first named mill. Hence it follows, that in such asystem of control the distribution of work is very uneven, the tensionof the material passing from one mill to the other fluctuatesconsiderably, and is usually either or other devices are controlledautomatically.

In other words, my improved system of speed control provides for anautomatic adjustment of the speed of one mill as the speed of the othervaries, so as to compensate entirely for the relative speed variatlonsof the mills with reference to the distribution between the latter ofthe total work of reduci tion. each performs a certain proportion of thetotal work, the ratio of the output of the respective mills will bemaintained automatically in spite of external influences and in Sliltflof variations in the gage of the meta rolled.

To these and other ends the invention consists in the novel system ofspeed control to be hereinafter described and claimed.

In the accompanying drawings,

Figure 1 is a side elevation of a rolling mill installation embodying myinvention, the respective stands of rolls being driven by electricmotors,

Fig. 2 is a top plan view of Fig. 1,

Fig. 3 is a diagram of the motor of one of the stands,

Fi shows in elevation a tandem rolling mill installation in which therespective mills are operated by steam engines,

Fig. 5 is' a to plan view of Fig. 4, and

Fig. 6 is a etail of the governor of one of the engines.

The improved system is applicable to rolling mills driven by electricmotors, steam engines, internal combustion en 'nes, and other motors orrime movers. e general principles are tli e same in each case, and I aveonly selected for illustration, embodiments in which electric motors andsteam engines, res ectively, are employed for drivin the m' a y eferringto Figs. 1 to 3, showing the electric motor arrangement or embodiment, Aand B indicate stands of rolls to act simultaneously on successiveportions of a bar or sheet of metal C passing from the mill A to Henceif the mills are adjusted so that the mill B, as indicated by thearrows. The mill A first acts on the bar or sheet and reduces it to acertain extent, and the reduced portion of the bar passes forwardly tobe further reduced by the mill B which is arranged in advance of themill A as regards the direction of feed. The mill or stand A is driven bmeans of an electric motor 10 geared to t e rolls in any suitable mannerand the mill B is similarly driven by means of an electric motor 11. Thespeed of the motor 10 is controlled manually by a controller or rheostat15 and the motor 11 is similarly controlled by a rheostat 12.

In the embodiment illustrated, the motor 11 is intended to represent ashunt wound motor operating at a substantially constant speed underfluctuating loads. On the other hand, the motor 10 for driving the millA is so wound, as distinguished from the shunt motor 11, as to decreasein speed and increase in torque in proportion to an increase in theload, and vice versa. In other words, the motor 11 for the mill B ispractically a constant speed motor, while the motor 10 of the mill Avaries in speed inversely in proportion to the load. In order to givethe motor 10 the characteristics above noted, I use by preference :1compound winding, as shown in Fig. 3, where the armature is indicated at13 and the field at 14. The field 14 comprises a shunt windin 14 and aseries winding 14!, the shunt w nding 14 being connected with therheostat 15 by means of which the speed of the motor 10 may be varied bythe operator. I prefer, in actual practice, to have the normal shuntwinding 14E constitute about per cent. of the total field winding, inwhich case the series winding 14 will only amount to about 20 per centBy this arrangement the motor retains practically all of the shunt motorcharacteristics which adapt it particularly for driving a stand ofrolls, and yet the series portion of the field is sufficient to causeenough speed variation in proportion to the load to efi'ect theoperation now to be described.

Supposing the bar or sheet of brass or other metal to be passing fromthe mill A to the mill B, so that it is successively reduced by therespective pairs of rolls, the mill B will be driven at a practicallyconstant speed, which is preferably so adjusted "with respect to thespeed of the mill A, that the mill B pulls the sheet or bar through therolls of the mill A to a slight extent, thereby assisting to a certainextent in theoperation of the mill A and relieving the motor 10 of acorresponding amount of work. If now the mill B be slowed down, forexample, by -any external influence, or by a decrease in the thicknessof the bar or sheet due to expansion of its rolls or hard spots in themetal, the pulling efl'ect of the mill B on the bar or sheet passingbetween the rolls of the mill A will be correspondingly decreased. Thiswill obviously put more work on the motor 10 of the stand A, andaccordingly, the influence of the series winding 14 of said motor willbe immediately called into play, with the result that the speed of themotor 10 will decrease approximately in proportion to the increase ofload produced by the decrease of speed of the mill B. Hence it will beunderstood that the decrease of speed of the mill B will be immediatelyfollowed by a substantially corresponding decrease of speed of the millA, the latter adapting itself automatically to the speed decrease of themill B in such a manner as to maintain the ratio of the reduction doneby the two mills. Supposing that the speed of the mill B be increasedfor any cause, the pulling'efiect of this mill on the bar or sheetpassing through the mill A will, of course, be correspondinglyincreased, thereby further relieving the motor 10, and as the load onthe latter decreases the efl'erl of the series winding 14 is immediatelytn produce a corresponding increase of speed to compensate for theincrease of speed of the mill B.

If at any time the mill A tends to roll the bar faster than the mill Bcan carry it, the former, mill will tend to push the bar through thelatter, thereby relieving the mill B of some of its work until the millA has slowed down on an equilibrium point.

It is not necessary in all cases that the. mill B be driven by anelectric motor, as it might be driven by other means while stillretaining the electric drive of the mill A. On the other hand, it is notalways essential that the variable speed characteristics mentioned abovein reference to the mill A be limited to said mill, as obviously aninterchange of the driving motors 10 and 11 as between the mills A and Bwould be within the broad aspects of my invention. In other .words, itmightbe practicable in some cases to have the mill A driven by aconstant speed motor and to have the mill B driven by a variable s eedmotor.

In Figs. 4 to 6 inclhsive, the relative arrangement of the mills A and Bis substantially the same as that previously described, but the mill Ais driven by a steam en ine 16 and the mill B by a steamengine l7. Theengine 17 is rovided with a governor 18 connected witih the throttle.valve 19 (or otherwise arranged) so. asto. maint In a practicallyconstant speed of the engine 17 and mill B under varying conditions ofload. This means 01, speed control by means of a fly-ball governor-is .avery common one, and hence need-not be described in detailr In order toprovide for the variable speed characteristics of the engine 16 theaction of the ball governor 20 thereof (connected with the throttlevalve 21 by means of the link 22) is opposed by a spring 23 whichprevents the governor from operating the throttle valve sufficiently tocompensate for variations of load, so that the speed of the engine 16will decrease as the load increases, and vice versa. In the embodimentshown, the governor 20 comprises the usual centrifugally acting balls 24acting on the usual sliding sleeve 25 to which is connected one end of abell crank lever 26 pivoted to a fixed part 27 and suitably connectedwith the throttle controlling link or rod 22. As the balls are loweredby a decrease of speed (due to an increase of load) they tend to carrydownward the collar 25 and to so actuate the valve rod 22 as to bringthe speed again up to the normal, but this tendency of the fly-balls 24is opposed by the sprin 22, interposed between the standard 28 and thefree extremity of the bell crank lever 26, so that the compensatingeffect of the governor is offset to a degree, with the result thatchanges of load will cause corresponding but inverse changes of s eed.

As the speed characteristics of t e engines 16 and 17 are substantiallythe same as those of the motors 10 and 11 heretofore described, it willbe obvious that the operation of the installation now being described,will be substantially the same as that of the first installation.Moreover, it will be manifest that the invention can be carried out insubstantially the same manner with as engines or other prime movershaving the characteristics above described. It is not necessary, in allcases, that the rime movers or motors of the respective mills or othermetal working devices have different speed and torque characteristics,so long as at least one of the motors changes its speed automaticallywith a change of load.

f course, I do not wish to limit myself in all of the various aspects ofmy invention, to the application of the present system to the tandemrolling of sheets or bars. I have used the term rolling mill in a broadsense intending to cover such an equivalent device as a wire drawingblock or other apparatus. It is, moreover, evident that the invention isnot limited to the use of two metal working devices arranged in tandem,as a larger number may be grouped together in some cases. Variouschanges in these and other respects may be adopted within the see c ofthe appended claims.

hat'I claim is:

1. In a tandem rolling mill installation the combination with therespective mills, o a separate prime mover for driving each of the same,and means controlled directly by variations of tension in the stockbetween the mills, independently of variations of length incident tosuch tension changes, for automatically varying the speed of i the primemover of one mill, to com ensate for speed variations of the other m1substantially as described.

2. The combination of metal working de vices arranged in tandem forsimultaneous operation on a length of stock fed by one of said devicesto the other, separate prime movers for said devices, and meanscontrolled by the direct action of the stock on one of said devices dueto variations of tension in that portion of the stock between saiddevices, and independently of changes of length in such portion incidentto such tension changes, for automatically and directly varying thespeed of one of said devices to compensate for the speed changes of theother.

3. The combination with metal reduction devices arranged in tandem forsimultaneous action on successive portions of a length of stock, ofindividual prime movers to drive the res ective devices, one of saidprime movers eing adapted to so operate the correspondin meta reducingdevice that it will pull t e stock through the other metal workingdevice, and at least one of said rime movers being constructed todecrease in speed with an increase of load caused directly by a chan eof tension in that portion of the stock in t e interval between saidreduction devices, said prime mover being constructed to vary its speedindependently of variations of length of that portion of the stock inthe interval between said devices incident to the aforesaid tensionchanges.

4. The combination with metal reduction devices arranged in tandem forsimultaneous action on successive ortions of a length of stock fed fromone of said devices to the other, of prime movers for driving therespectlve devices individually, one of said devices being so driven asto pull the stock through the other to a certain extent, whereby thetension in the material between the two devices acts to transfer workfrom one of the prime movers to that of the other device, the primemover of such following device being constructed and arranged todecrease in speed with an increase of load independently of changes inthe length of the stock incident to an increase of load, substantiallyas described.

5. The combination of rolling mills arran in tandem, means to drive oneof said mil s at a substantially constant speed, and an electric motorfor driving the other mill, having a compound Winding, whereby saidmotor varies in speed with a variation of load to compensate for speedvariations of the first mill; substantially as described.

6. The combination of rolling mills arran ed in tandem, of means todrive one of sairf mills at a substantially constant speed, and anelectric motor for driving the other mill, having a relatively largeshunt field winding, and a relatively small series field winding,whereby the speed of such last mentioned mill is automatically varied tocompensate for speed chan s of the first mill; substantially as descried.

7 The combination of metal working devices arranged in tandem forsimultaneous operation on a length of stock which passes from one ofsaid devices to the other, means for driving the second device atpractically a constant speed, and a motor for driving the first devicewhichvaries in speed with a variation of loadand is directly controlledby the variable tension on the stock, independently of chan es in thelength of the stock incident to t e tension changes; substantially asdescribed.

8. The combination of metal working def. vices arranged in tandem forsimultaneous operation on a length of stock fed from one of said devicesto the other, means for driving the second device at a practicallyconstant speed, and an electric motor for driving the first device,having a series field winding whereby it is adapted to decrease in speedwith an increase of load; substantially as described.

9. Apparatus for operating on material of the kind described, comprisinga plurality of elements havin passes to simultaneously act on several dierent parts of the same piece of material, and means to feed thematerial through the passes, comprising an electric motor for each pass,at least one of said motors being so Wound as to decrease in speed withan increase of load whereby electric motor, said motor so wound thetension of the material being operated on directly and automaticallycontrols the speed of the motors.

10. The combination of metal reducing devices arranged in tandem forsimultaneous action on successive portions of a length of stock fed byone of said devices to the other, and separate prime movers for drivingthe respective devices independently, at least one of said prime moversconstituted by an electric motor which is wound to vary its speeddirectly and automatically as a result of variations in the tensionofthe stock in the interval between said reducing devices, whereby saidelectric motor varies the speed of its reducing device to correspondwith speed variations of the other reducing device; substantially asdescribed.

11. The combination of metal working devices arranged in tandem forsimultaneous operation on a length of stock fed by one of said devicesto the other, a prime mover for driving one of said devices, an electricmotor for driving the other device, and adjustable means for controllingthe speed of said as -to decrease in speed with an increase of ldad onits reducing device without actuation of said speed controlling means,whereby the speeds of the reducing devices are directly andautomatically controlled by variation of the tension of the stock;substantially as described.

12. The combination of metal reducing devices arranged in tandem forsimultaneous action on successive portions of a length of stock fed byone of such devices to the other, and electric motors for driving therespective devices individually, so wound as to maintain automatically apredetermined speed ratio between said devices by the tension in thestock; substantially as described.

13. The combination of metal reducing devices arranged in tandem forsimultaneous action on a length of stock, electric motors for drivingthe respective devices individually, so wound as to maintainautomatically a predetermined speed ratio between said devices, andmanually adjustable resistance means for controlling the speed of saidmotors; substantially as described.

14. The combination of metal reducing devices arranged in tandem forsimultaneous action on a length of stock, prime movers for therespective devices, one of said prime movers being adapted to drive itsreducing device at such speed as to pull the stock through the otherdevice and thereby tension the stock to a certain extent, the primemover of such other device being constituted by an electric motor havinga compound winding whereby it is adapted to decrease its speedautomatically with an increase of load due to a decrease of such tensionof the stock, and variable resistance means for varying the speed ofsaid compound wound motor; substantially as described.

15. The combination of metal reducing devices arranged in tandem forsimultaneone action on successive portions of a length of stock, saiddevices having rotary parts adapted to feed the metal forward during thereduction thereof, separate prime movers for driving said rotary arts ofthe respective devices, and means For operativel connecting each primemover with its re ucing device, at least one of said prime movers be inggeared directly to its reducing device and said prime mover being soconstructed and arranged as to vary the speed of said remover fordriving the other device, gear ng connectin one of the devices with itsrime said other device from its prime mover, and 40 moverso t theformerls positivel driven, manually operable means for directly con;

' said prime mover being construe and artrolling the speed of said primemovers, said ranged to vary its speed directly and autolast-named primemover bei constructed a matically bye variation in load transmltted anda to vary its spec? by said gearing to said prime mover whenautomatically'byvariations of tension in the 48 the stock undergoes achange of tension, instock transmitted to it through saidtransdependentl of a change of length in the mission mechanism, and indedentl of length of e stock inci ent to such tension said m nually Repe-able ntra log change, and se arate manuall operable means and ofchanges in length of the etoo means for y controlling t eepeed ofincident to ension cha such prime movers independently of the ten 19.The combination of metal reducing sion m the stock. devices arranged intandem for simultaneous 17. The combination of metal reducing deactionon a length of stock a prime mover vices arranged in tandem forsimultaneous for driving one of said evices, aprime operation on alength of stock fed by one of mover for the other device consist' of ansaid devices to the other, a prime mover forelectric motor, gearing forpositively living-one of said devices, a prime mover such other devicefrom said electric motor, for driving the Other device, gearing 0011-and adjustable means for directly controlnecting one of the devices'with its prime ling the speed ofsaid primemovergsaidelecmoverso thatthe former is positivel driven, tric motorheing constructed and a saidprime mover beingdcianstru and arto-decreasle its spear: witllllandincrease 0; load ranged to-vary its ee ireetly an autoimposedtt emont oug sai rlng' yva s2 transmitted riation oftension'in the stock infidependently by said gearing to said prime mover when of saidadjustable eed controlling means the Stock undergoes a change oftension, inand ot variations'of engths incident to tendependently of achange oflength 1n the S1011 changeswhereby the speed ofoneofeaid ion ofStock. incident to such devices is automatically changed to com ena J men lltllly operable sate for speed changes of the other, sai ad- 6 P d'f justablecontrolling means and said autosue time moversindependently ofthe ten matic control being adapted for eimultane- 7.

" devices rranged in tandem for the. Sim?!- mon 1n the stock while theautomatic oonous operation. a

' V In witness whereof, I have hereunto let tion of metal a we my(handpn the 20th y of August, 1912.

taneousoperationonalengthof a 1 j pnm mover for driving one oft-raiddevices, Witnr arune mover for the other devi trans- E. .n u s sion mfor positively driving M. 0m: 1 7mm.

